This nonprovisional application claims priority under 35 U.S.C. xc2xa7119(a) on Patent Application No. 2000-358247 filed in Japan on Nov. 24, 2000, which is herein incorporated by reference.
(1) Field of the Invention
The present invention relates to a toner cartridge for storing fresh toner for development therein, and attached to, and used for, a developing unit of an image forming apparatus such as a copier, printer, facsimile machine and the like. More detailedly, the invention is directed to a toner cartridge wherein a collecting chamber for collecting untransferred toner left over on the photoconductor surface after transfer of toner images is arranged on one side of the storage chamber of the fresh toner, as well as relating to an image forming apparatus using this toner cartridge.
(2) Description of the Prior Art
Image forming apparatus such as a copier, printer, facsimile machine and the like form images by an exposure step where exposing the surface of a photoconductor such as a photoconductor drum, photoconductor belt or the like, to light forms a desired electrostatic latent image, a development step for making the thus formed static latent image visible with toner, a transfer step for transferring the formed toner image to the predetermined paper and a fixing step for fixing the transferred toner image on the paper with heat. The exposure, development and transfer steps are sequentially performed by the exposure unit, developing unit and transfer unit, respectively, all being arranged around the photoconductor.
The developing unit has a developer roller which is closely opposed to the photoconductor surface and rotates about an axis parallel to that surface. The toner for development is adapted to uniformly adhere to the whole surface of the developer roller on the side opposite to the photoconductor, is conveyed by the rotation of the developer roller and attracted to the latent image on the photoconductor surface by the function of static electricity. In such a developing unit, the toner is consumed by its adherence to the photoconductor so that the toner needs to be supplied. This supply is performed by fitting a toner cartridge that stores an appropriate amount of toner to the mount adaptively designed to the developing unit.
Part of toner attracted to the photoconductor surface from the developing unit is untransferred to the paper at the subsequent, transfer unit and remains thereon. Such untransferred toner needs to be removed from the photoconductor surface and collected before the next cycle of exposure and development. For this purpose, use of a toner cartridge for toner supply has been conventionally made in which a toner storage chamber for storing fresh toner and a toner collecting chamber arranged on one side of the toner storage chamber with a partitioning wall in between so that the untransferred toner collected from the photoconductor is kept in the toner collecting chamber and the collected untransferred toner can be disposed of when the toner cartridge is replaced for supplying the toner.
In a toner cartridge of this type, the volume of the toner collecting chamber is determined based on the expected amount of untransferred toner to arise during transfer. However, the actual amount of untransferred toner to be collected varies depending on usage and environmental conditions such as variations in toner charge performance, print paper types and the like. In addition, when, for example, jamming of print paper (paper jam) occurs, the toner adhering on the photoconductor surface at that point is collected in its entirety as the untransferred toner. Thus, there is a risk that the actual amount may markedly increase due to occurrence of inevitable malfunctions.
Under these circumstances, the volume of the toner collecting chamber needs to be designed to be large enough so as to be on the safe side of the expected amount of untransferred toner generated, giving priority to prevention of the collected untransferred toner leaking outside. This therefore results in a large configuration of toner cartridge, giving rise to a problem of constraint on the design flexibility of the image forming apparatus due to reservation of the attachment space of the toner cartridge.
Various proposals have been made in order to solve this problem. FIG. 1 is a perspective view showing an image forming apparatus configuration disclosed in Japanese Patent Application Laid-Open Hei 4 No.237079. This image forming apparatus includes a toner cartridge comprised of a toner storage chamber (toner container) 101 for storing fresh toner, a toner collecting chamber (waste toner container) 102 for collecting untransferred toner on one side of the toner storage container, a partitioning wall 103 for separating these chambers and a toner passage window 104 formed on the wall and sealed by a shutter which is opened by the force acting from the toner collecting chamber 102 side.
In the drawing, 105 designates a photoconductor drum and 106 designates a cleaning unit for removing untransferred toner left over on the peripheral side of photoconductor drum 105 after transfer. This cleaning unit 106 is connected to toner collecting chamber 102 by way of a collecting pipe 107 incorporating a coil wire as a conveyer means. The untransferred toner removed by cleaning unit 106 is conveyed into toner collecting chamber 102 passing through the collecting pipe 107 and kept in the toner collecting chamber 102.
According to this configuration, if the collected amount of untransferred toner increases and toner collecting chamber 102 has become full of toner, the shutter that seals the toner passage window 104 as an opening of partitioning wall 103 is released by the pressure of the untransferred toner, applied from the toner collecting chamber side 102 so that part of the untransferred toner in toner collecting chamber 102 returns to toner storage chamber 101 via toner passage window 104. Accordingly, it is possible to prevent untransferred toner from leaking outside while keeping the volume of toner collecting chamber 102 small, thus alleviating the aforementioned problem.
The untransferred toner returned to toner storage chamber 101 is mixed with the fresh toner and reused. In this case, the untransferred toner is unstable with regard to its charge characteristics and may cause degradation of image quality due to its reuse, but the influence on the image quality is small when the amount of return is trivial.
As already stated above, in this configuration, the shutter that seals toner passage window 104 is adapted to be released by the pressure of the untransferred toner collected in toner collecting chamber 102. In order to assure this opening action and make the untransferred toner move smoothly, it is necessary to provide optimal design of the shutter opening and closing mechanism and optimal arrangement of the opening position of toner passage window 104. When an insufficient amount of untransferred toner is returned, there is a possibility of the untransferred toner in toner collecting chamber 102 leaking outside. In contrast, when an excessive amount of untransferred toner is returned, there is the aforesaid problem that degradation of image quality due to the reuse is inevitable.
FIG. 2 is a perspective view showing a configuration of an image forming apparatus disclosed in Japanese Patent Application Laid-Open Hei 8 No.44179. This image forming apparatus includes a toner cartridge comprised of a toner storage chamber (supply toner reservoir) 111 for storing fresh toner, a toner collecting chamber (waste toner reservoir) 112 for collecting untransferred toner on one side of the toner storage chamber, a partitioning wall 113 for partitioning these chambers and a conveyer auger 114 extending across these two chambers, penetrating through the partitioning wall 113.
When this toner cartridge is attached to the predetermined position of the image forming apparatus, toner collecting chamber 112 is connected to a toner collecting pipe 116 via a toner collecting port 115 which opens on the top face at one side (the side farthest from toner storage chamber 111) while toner storage chamber 111 is connected to an unillustrated developing device via a toner supply port 117 which opens on the bottom face at the other side (the side farthest from toner collecting chamber 112). Auger 114 is coupled to a drive source inside the image forming apparatus so that it axially rotates by the driving force from the drive source.
In this toner cartridge, the fresh toner inside toner storage chamber 111 is conveyed toward toner supply port 117 as indicated by the arrow E in the drawing whilst it is being agitated by the rotation of auger 114 so that the toner is supplied to the developing device through toner supply port 117. The untransferred toner removed from the unillustrated photoconductor surface after transfer is collected through toner collecting pipe 116 and toner collecting port 115 into toner collecting chamber 112. The thus collected toner is conveyed in the toner collecting chamber 112 by auger 114 toward partitioning wall 113 which keeps the collecting chamber away from toner storage chamber 111, as indicated by the arrow F, so that the toner will be stacked successively from the toner storage chamber 111 side or from the side farthest from toner collecting port 115.
According to this configuration, the untransferred toner collected in toner collecting chamber 112 is kept efficiently, being evenly distributed inside toner collecting chamber 112. That is, it is possible for even a toner collecting chamber 112 of a small volume to collect a higher amount of untransferred toner therein, thus alleviating the above-mentioned problem. A configuration of enhancing the collecting efficiency by arranging a conveyer means inside the toner collecting chamber in the same way as above except for a variational conveyer means is disclosed in, for example, Japanese Patent Application Laid-Open Hei 5 No.341697.
However, in this configuration, it is impossible to collect untransferred toner in an amount markedly exceeding the volume of toner collecting chamber 112. In order to deal with a sharp increase in the amount of untransferred toner unexpectedly generated due to occurrence of malfunctions, it is necessary to design the volume of toner collecting chamber 112 so as to be large enough therefor, which makes it impossible to fully meet the demand for reduction in size of toner cartridges.
The untransferred toner introduced into toner collecting chamber 112 is conveyed by a conveyer means such as auger 114 or the like and is stacked whilst being successively pressed against partitioning wall 113 that keeps the collecting chamber away from toner storage chamber 111. As a result, the drive load on the conveyer means sharply increases with increase in the collected amount. In particular, when auger 114 as a conveyer means is also used for the agitator and conveyer means for the fresh toner inside toner storage chamber 111 as shown in FIG. 2, the sharp increase in drive load may obstruct fresh toner supply to the developing device and there is even a risk of deteriorating image quality.
The present invention has been devised under the above circumstances, and it is therefore an object of the present invention to provide a toner cartridge which is markedly compact compared to conventional toner cartridges and can collect untransferred toner removed from the photoconductor, adequately enough to deal with increase in the amount of untransferred toner attributed to abrupt malfunctions, but in a range in which degradation of image quality will not occur, whilst keeping the volume of a toner collecting chamber arranged on one side of a toner storage chamber as small as possible. The present invention is also directed to an image forming apparatus using this toner cartridge.
In order to achieve the above object, the present invention is configured as follows:
First, the first aspect of the present invention resides in a toner cartridge comprising: a toner storage chamber for storing fresh toner; a toner collecting chamber disposed on the side of, and separated by a partitioning wall from, the toner storage chamber, for collecting the untransferred toner removed from the photoconductor; a toner passage disposed at a predetermined height penetrating through the partitioning wall and establishing communication between the toner storage chamber and the toner collecting chamber; and a toner conveyer means disposed inside the toner passage for conveying the untransferred toner input from the toner collecting chamber side toward the toner storage chamber.
In accordance with the second aspect of the present invention, the toner cartridge having the above first feature is characterized in that the toner passage is configured of a pipe-like passage having openings at both ends for allowing communication between the toner storage chamber and toner collecting chamber, and the toner conveyer means is configured of a rotor that rotates about the axis inside the pipe-like passage to convey the untransferred toner.
Next, in accordance with the third aspect of the present invention, the toner cartridge having the above first feature is characterized in that a sealing element or a pair of sealing elements removably attached are provided for the passage opening or openings at one or both ends of the toner passage.
In accordance with the fourth aspect of the present invention, the toner cartridge having the above first feature is characterized in that a sealing element or a pair of sealing elements are provided for the passage opening or openings at one or both ends of the toner passage and are adapted to move to release the passage opening or openings in linkage with the action of the toner conveyer means.
Finally, the fifth aspect of the present invention resides in an image forming apparatus comprising: a developing unit for making the electrostatic latent image formed on the photoconductor visible; a transfer unit for transferring the toner image developed by the developing device to the printing material; a cleaning unit for removing the untransferred toner remaining on the photoconductor surface after transfer by the transfer unit; a toner cartridge removably mounted to a position so as to be associated with the developing unit and cleaning unit, in order to supply the fresh toner stored in a toner storage chamber to the developing unit and collect the untransferred toner removed by the cleaning unit into the toner collecting chamber, wherein the toner cartridge comprises: a toner storage chamber for storing fresh toner; a toner collecting chamber disposed on the side of, and separated by a partitioning wall from, the toner storage chamber, for collecting the untransferred toner removed from the photoconductor; a toner passage disposed at a predetermined height penetrating through the partitioning wall and establishing communication between the toner storage chamber and the toner collecting chamber; and a toner conveyer means disposed inside the toner passage for conveying the untransferred toner input from the toner collecting chamber side toward the toner storage chamber.
In the present invention, the untransferred toner removed from the photoconductor surface after the transfer step is collected in the toner collecting chamber and stacked therein, and when the stacked amount reaches the predetermined upper limit level, the toner enters from one end of the toner passage, formed at the predetermined height corresponding to this upper limit level, penetrating through the partitioning wall that keeps the collecting chamber away from the toner storage chamber and is conveyed toward the toner storage chamber by the action of the toner conveyer means so as to be returned at the other end into the toner storage chamber. If the upper limit level is determined so as to correspond to the expected amount of untransferred toner, only the untransferred toner exceeding this expected amount is introduced into the toner passage and returned to the toner storage chamber, thus providing simple control of the return amount. Therefore, it is possible to keep the volume of the toner collecting chamber as small as possible and collect the untransferred toner removed from the photoconductor adaptively and adequately including any increment due to abrupt malfunctions.
Further, in the present invention, a pipe element penetrating through the partitioning wall between the toner storage chamber and toner collecting chamber is arranged as the toner passage while a toner conveyer means (waste toner conveyer device) that rotates about the axis inside the toner passage is arranged. Thereby, as this waste toner conveyer device rotates, the untransferred toner (waste toner) introduced into the toner passage is assuredly conveyed and returned into the toner storage chamber.
Also, in the present invention, the passage opening or openings at one or both ends of the toner passage are covered with a removable sealing element or elements so that the fresh toner stored in the toner storage chamber is prevented from flowing back to the toner collecting chamber by way of the toner passage during handling from its manufacture till its setting into the image forming apparatus.
Further, in the present invention, the passage opening or openings at one or both ends of the toner passage are covered with a sealing element or elements so that the fresh toner stored in the toner storage chamber is prevented from flowing into the toner collecting chamber by way of the toner passage during handling from its manufacture till its setting into the image forming apparatus. In addition, the sealing element or elements are opened in linkage with the action of the toner conveyer means after the cartridge has been set into the image forming apparatus, so as to open the passage openings to thereby allow untransferred toner to return.
Finally, the present invention provides a compact image forming apparatus configuration which is free from toner leakage and degradation in image quality by using a compact toner cartridge of the present invention which can be removably attached into the mounted position in association with the developing unit consuming the fresh toner and the cleaning unit removing untransferred toner and has a toner collecting chamber of a minimum volume but which is enough to realize reliable collection of untransferred toner.